//var rem = window.innerWidth/750;
//var docEl = document.documentElement;
//var fontEl = document.createElement('style');
//docEl.firstElementChild.appendChild(fontEl);
//fontEl.innerHTML = 'html{font-size:1rem=' + rem + 'px;}';

var rem = window.innerWidth*100/750;
var docEl = document.documentElement;
var fontEl = document.createElement('style');
docEl.firstElementChild.appendChild(fontEl);
fontEl.innerHTML = 'html{font-size:' + rem + 'px;}';
console.log(docEl)
console.log(rem)
